Add test cases for delete command and payment status field

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...va/seedu/address/logic/commands/DeleteCommand.java	80.00%	0 Missing and 1 partial :warning:

Files with missing lines	Coverage Δ	Complexity Δ
...va/seedu/address/logic/commands/DeleteCommand.java	97.87% <80.00%> (+49.03%)	17.00 <0.00> (+9.00)

... and 7 files with indirect coverage changes